Endovascular graft wih separable sensors

ABSTRACT

A endovascular graft having sensing devices attached thereto to facilitate measurement of pertinent parameters within the vasculature into which the graft is implanted. Power sources and transmitters may be attached to the graft to facilitate transmission of measurements to a receiving device outside the patient&#39;s body. The sensing devices, may be electrically passive or integrated devices with measurement and transmission capability. The sensing devices may be attached to specific locations on the graft material or attached to the lumen, thereby providing pertinent parameters from critical points inside the vasculature, or may be dispersed over the surface of the graft material or within the lumen to provide a profile of pertinent parameters. The sensing devices may be attached to the graft material with one suture using a running stitch to minimize graft bulk and may be coated with a material to inhibit or control tissue growth. A bio-reabsorbable or hard wire tether or suture may be employed to attach devices to one or more graft components.

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 10/165,763, filed Jun. 7, 2002.

BACKGROUND OF THE INVENTION

[0002] This invention relates to the treatment of body lumens and, moreparticularly, to the endovascular placement of a prosthetic graft withinvasculature for the purpose of repairing the same.

[0003] Ruptured abdominal aortic aneurysms (AAA) are a leading cause ofdeath in the United States. Treatment options to repair AAA includeconventional open surgery and implantation of an endovascular graft.Conventional open surgical repair of AAA involves major abdominalsurgery with associated high rates of morbidity. Endovascular graftshave been developed to endoluminally bypass abdominal aortic aneurysmsthrough minimally invasive surgery. Many patients that are unacceptablesurgical risks for open repairs are eligible for endovascular graftimplantation. Deployment of transfemoral, endovascular grafts to treatAAA is appealing for many reasons: avoidance of an abdominal incision,lack of aortic cross clamping, the potential for regional anesthesia,and a shortened hospital stay.

[0004] Untreated AAA have been shown to continue to expand untilrupture, with an associated high mortality rate. Implantation ofendovascular grafts have also been associated with high complicationrates, including perioperative death, conversion to open repair, theneed for further intervention, the need for hemodialysis, a failure tocure the AAA, and wound complications.

[0005] The inability to obtain or maintain a secure seal between thevessel wall and the endovascular graft is a complication unique toendovascular aneurysm exclusion. Because the term “leak” has beenassociated with aneurysm rupture following conventional surgery, theterm “endoleak” has been proposed as a more definitive description ofthis complication. It is believed that persistent endoleaks result incontinued aneurysm expansion, which may eventually lead to aneurysmrupture. Aneurysms that have been successfully excluded have shown atendency towards a reduction in aneurysm diameter. Failure to properlyexclude the aneurysm from systemic arterial blood pressure keeps thepatient at risk of impending rupture. Endoleaks have been classifiedaccording to the source of the leaks. Current classifications ofendoleaks include four categories. Type I endoleaks are “perigraft” or“graft-related” leaks that involve a persistent channel of blood flowdue to inadequate or ineffective sealing at the ends of the endovasculargraft, or between overlapping components of a modular system. Type IIendoleaks are retrograde flow into the aneurysm sac from patent lumbararteries, the inferior mesenteric artery, or other collateral vessels.Type III endoleaks result from fabric tears, graft disconnection, orgraft disintegration. Finally, Type IV endoleaks are flow through thegraft fabric associated with graft wall porosity or permeability. It hasbeen recognized that preoperative patent side branches are not a goodpredictor of postoperative endoleaks.

[0006] There have been a number of reported cases of aneurysm rupturefollowing implantation of an endovascular graft. Some of the rupturesoccurred in patients without a documented endoleak.

[0007] A number of studies have focused on measurement of pressurewithin the aneurysm sac following implantation of an endovascular graft,both in the human patient, an animal model, or an in vitro model.Properly implanted endovascular grafts have been shown to reduce thepressure within the aneurysm sac while an endoleak, with or withoutdetectable blood flow, continues to pressurize the sac at pressuresequivalent to the systemic arterial pressure. Animal studies utilizing apredictable rupturing aneurysm model have shown that non-excludedaneurysms will rupture. Thrombosed aneurysm sacs may still receivepressurization from a sealed endoleak and this continued pressurizationkeeps the aneurysm at risk for rupture.

[0008] Current methods of patient follow-up include arteriography,contrast-enhanced spiral computed tomography (CT), duplexultrasonography, abdominal X-ray, and intravascular ultrasound. All ofthese methods are costly and involve invasive procedures with associatedmorbidity that may need to be performed in a hospital. None of theimaging methods are completely successful in detecting endoleaks.Therefore, the potential exists for an endoleak to go undetected untileventual rupture. An increase in aneurysm diameter is detectable, andshould be considered an indication of endoleak. To avoid aneurysmrupture an increase in aneurysm diameter must be detected in a timelyfashion to identify patients in need of corrective endovascularprocedures.

[0009] An endovascular graft with the ability to measure pressure withinthe aneurysm sac and provide feedback to the physician could provideacute confirmation of a procedure and identify those patients withpersistent pressurization of their aneurysm, and subsequent risk ofrupture. Some physicians are advocating that the follow-up examinationsof AAA patients focus on pressure measurements, but that this is notcurrently clinically feasible. Furthermore, follow-up examinations maybe performed in the physician's office as opposed to a hospital.Moreover, clinicians will have a new method to study the pathology ofpost-endovascularly treated AAA disease.

[0010] Accordingly, there exists a need for an endovascular graft thatfacilitates non-invasive measurement of pressure, as well as otherpertinent parameters, within the aneurysm sac and along the endovasculargraft itself as a means for confirming the success of a procedure aswell as identifying patients at risk for aneurysm rupture after theendovascular graft is implanted.

[0011] However, providing devices on an endovascular graft to facilitatethe measurement of pertinent parameters poses problems. The measurementdevice increases bulk, which can significantly effect the deliveryprofile of the endovascular graft and increase the force necessary todeploy the device, such as jacket or release wire retraction forces.Increased bulk is a significant issue for an endovascular graft.Furthermore, attachment of measurement devices to an endovascular graftmay require sutures and the suture knots not only provide increasedbulk, but are also potential graft wear points. Additionally, tissuegrowth around a measuring device attached to an implanted endovasculargraft may interfere with its function and inaccurate data may result.The present invention addresses these problems and other needs.

SUMMARY OF THE INVENTION

[0012] Briefly and in general terms, the present invention is embodiedin an endovascular graft with sensors attached thereto. The endovasculargraft has the ability to be delivered endovascularly and measurepertinent parameters within the lumen in which it is implanted. Theendovascular graft has the ability to transmit data about intra-lumenparameters to an external monitoring device. Confirmation of asuccessful implant procedure is quickly and easily obtained. Patientfollow-up is less costly (conducted in the physician office),non-invasive, and more accurate, allowing prompt intervention in thosepatients most at risk for acute AAA rupture. The invention would alsoallow for more frequent patient follow-up, increasing the potential todiagnose and treat aneurysms at risk before acute rupture.

[0013] In one aspect of the invention, a modular endovascular grafthaving a main body component and one or more limb components isprovided. One or more sensors are attached to the limb component(s). Byattaching at least one sensor near the superior end of the limbcomponent and sizing the main body component such that the sensor isadjacent to the aneurysm sac when the endovascular graft is implanted,measurement of pertinent parameters within the aneurysm sac isfacilitated. The meaning of the term “adjacent” as used hereinencompasses the sensor being located within the aneurysm sac or at alocation where the parameters or properties being detected indicateconditions within the aneurysm sac. Measurements of pertinent parameterswithin the aneurysm sac may allow early confirmation of a successfulprocedure and identification of areas of the patient's vasculature atrisk for aneurysm rupture, thrombus formation, infection, inflamation orother anomalies without the need for invasive procedures.

[0014] An antenna or other data transmitter and a power source also maybe attached to the limb component adjacent to the aneurysm sac, allowinga physician or technician to monitor graft and vessel health without theneed for an invasive procedure. The transmitter transmits measurementsmade by the sensors to a receiver located outside the patient's body.With the main body component unencumbered with sensors, transmitters orpower sources, the bulk of the main body component is minimized andthereby, catheter diameter, jacket retraction and deploymentcomplications are kept to a minimum.

[0015] In another aspect of the invention, an endovascular graft isprovided that has attached thereto at least one integratedsensor/transmitter device capable of measuring a pertinent parameter andtransmitting the measurements to an external monitoring device. Althoughhaving more bulk than a sensor, the integrated sensor/transmitter devicehas less total bulk than a sensor and independent transmitter device,thereby facilitating less total bulk for the endovascular graft.

[0016] Furthermore, the integrated sensor/transmitter device may bedesigned to allow one or more “satellite” sensors, having no functionother than measurement, to be connected thereto. A single integratedsensor/transmitter device and smaller “satellite” sensors facilitate asmaller total bulk than multiple integrated sensor/transmitter devices.Attaching the integrated sensor/transmitter at a central location suchas the graft crotch and “satellite” sensors at various locations on theendovascular graft facilitates measurement and transmission to anexternal monitoring device of pertinent parameters at multiple locationsalong the endovascular graft and within the lumen. The “satellite”sensors allow a complete profile of pertinent parameters to be obtainedand may provide more accurate identification of anomalies. Measurementof pertinent parameters at multiple locations along the endovasculargraft or within the aneurysm sac may allow early detection of adefective seal between endovascular graft components, graft wear orchanges in aneurysm geometry. The smaller “satellite” sensors may alsoallow pertinent parameters to be measured from locations on theendovascular graft where local graft bulk is a constraint of the design,such as the graft contra limb or near the superior attachment systemthat holds the graft in the patient's aorta.

[0017] Additionally, it is contemplated that “satellite” sensors may beattached directly to the lumen of a patient. The integratedsensor/transmitter device also may be attached directly to the lumen orattached to an implanted endovascular graft.

[0018] Moreover, it is contemplated that passive devices, or monuments,which perform no sensing function may be attached to the implantedendovascular graft or directly attached to the aneurysm sac. By trackingthe location of the monuments with a monitoring device, changes in theposition of the endovascular graft within the lumen or changes in thegeometry of the tissue outside the endovascular graft may be detectedwithout the problems of encapsulation or thrombus isolation associatedwith the measurement of pertinent parameters. Such changes may provideearly detection of endovascular graft displacement or aneurysmre-dilation due to an endoleak.

[0019] Sensors with pressure measurement capability may be used todetect pressure changes in the aneurysm sac indicative of graft failureor endoleak due to an inadequate seal between the endovascular graft andthe vasculature. Sensors with temperature measurement capability may beused to detect temperature differentials associated with “hot spots”related to inflamation, infection or thrombus formation in the vessel.Sensors with the capability to measure oxygen and other bloodconstituents such as enzymes, proteins, and nutrients, may be used todetect minute blood flow indicative of endoleak. Sensors with thecapability to measure electrical potential or magnetic fields may beused to detect differences in potential associated with areas of thevessel at risk for thrombus formation. Sensors also may be provided tofacilitate other sensing applications such as blood oxymetry, bloodglucose, blood or fluid flow, biochemical or hormonal balance, bloodchemistry, positional data, dynamic displacement data, ocular pressure,respiration, electro physiology, tissue stress, venous return and bodyacoustics.

[0020] In yet another aspect of the invention, sensors are attached toan endovascular graft using one continuous suture. Starting at onelocation on the sensor, a running stitch around the sensor is used toattach the sensor to the graft fabric, thereby minimizing the number ofknots necessary for attachment, in this case a single knot. It iscontemplated that the running stitch may start at any location on thesensor depending on the location of the sensor on the endovasculargraft. Minimizing the number of knots is advantageous because knots arepotential graft wear points and add bulk. Additionally, a single knotattachment design may allow the sensor to be placed close to the graftcrotch due to the lack of a knot at the end closest the crotch.

[0021] In an additional aspect of the invention, the sensors may becovered in a coating that either inhibits tissue growth or promotes aknown or controlled amount and/or type of tissue growth. Because tissuegrowth may interfere with the ability of a sensor to perform itsmeasurement function, inhibiting tissue growth or restricting tissuegrowth to a known type and/or amount may increase the reliability ofmeasurements obtained.

[0022] In addition to being attached directly to a graft component, anintegrated sensor/transmitter, a sensor, a satellite sensor or amonument device incorporating one or more of the previously describedidentifying, observing, transmitting or measuring functions can beattached to a graft component via a bioreabsorbable suture or tether.Such devices are also contemplated to be attached to a graft componentvia a hard wire or other tether that functions to place the device in aposition separate from the graft and in desired circumstances, maintaina space between the graft component and the identifying, observing,transmitting or measuring device.

[0023] The invention is applicable to all applications of endovasculargrafts to treat aneurysmal segments of blood vessels. Furthermore, theinvention and methods disclosed herein may be applied any time it isdesired to measure intra-luminal parameters in a non-invasive manner. Itis contemplated that the invention may be used with all shapes ofendovascular grafts known within the art.

[0024] Other features and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a partial cross-sectional view of one embodiment of theinvention showing a partially assembled bifurcated endovascular graftimplanted across an aneurysm sac;

[0026]FIG. 2 is a perspective view of another embodiment of the presentinvention showing a bifurcated graft with an integratedsensor/transmitter device and “satellite” sensors;

[0027]FIG. 3 is a perspective view of a typical integratedsensor/transmitter device of the present invention;

[0028]FIG. 4 is a partial cross-sectional view of an alternateembodiment of the invention shown in FIG. 2 showing a bifurcated graftimplanted across an aneurysm sac into which an integratedsensor/transmitter device and “satellite” sensors have been attached;

[0029]FIG. 5 is a schematic view of another embodiment of the presentinvention showing an endovascular graft with monuments attached theretoimplanted in a patient's body and an external source/receiver;

[0030]FIG. 6 is an enlarged view of a portion of graft fabric showing asensor of the present invention attached using a single suture andrunning stitch;

[0031]FIG. 7 is a partial cross-sectional view, depicting anidentifying, observing or measuring device attached to a graft componentby a bio-reabsorbable or hard wire tether or suture; and

[0032]FIG. 8 is a partial cross-sectional view, depicting the tether ofFIG. 7 partially being reabsorbed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] As shown in the exemplary drawings and for purposes ofillustration, the invention is embodied in a prosthetic endovasculargraft having the ability to measure pertinent parameters inside thelumen into which it is implanted and transmit the measurements to areceiver located external to the patient.

[0034] Referring to FIG. 1, an embodiment of the invention is shown inwhich a modular bifurcated endovascular graft 10 of the type knownwithin the art is implanted in a body vessel 40 across an aneurysm sac42 in the area of the contra-lateral 44 and ipsi-lateral 46 iliacarteries using methods known within the art (only the contra-laterallimb is shown). The bifurcated endovascular graft 10 may be assembledin-vivo from a tubular trunk component 20 and two limb components 30.The trunk component 20 has a superior end 22 adapted to be secured abovethe aneurysm and an inferior end 24 adapted to accept the limbcomponents 30. The limb component 30 has a transmitter 12, power source14, and sensors 16 attached external the graft material. The transmitter12, power source 14 and sensors 16 can be integrated into one device asdescribed below. The limb component 30 has a superior end 32 adapted tomate with the trunk component 20 inferior end 24 and an inferior end 34adapted to be secured to the ipsi-lateral 44 iliac artery.

[0035] The sensors 16 measure pertinent parameters outside theendovascular graft 10 and the power source 14 provides power for thetransmitter 12 which transmits the measurements to a receiver (notshown) located outside the patient's body. The transmitter 12, powersource 14 and receiver (not shown) may be of any type known in the artof surgical implants or other systems utilizing miniaturized powersources and transmitters. The power source 14 and transmitter 12, forexample, may be of the type used in pacemaker technology or passivepower sources such as ultrasonic chargeable capacitors.

[0036] One or more sensors 16 are located near the superior end 32 ofthe limb component 30 but inferior the attachment/sealing area 26between the trunk component 20 and limb component 30 such that the sealbetween the trunk component 20 and limb component 30 is not jeopardized.Note that the attachment/sealing area 26 is such that one or more of thesensors 16 on the limb component 30 is adjacent the aneurysm sac 42,thereby facilitating measurement of pertinent parameters within theaneurysm sac 42 without encumbering the trunk component 20 with sensors16. Note also that the transmitter 12 and power source 14 are attachedto the limb component 30 such that they are also adjacent the aneurysmsac 42. Minimizing the bulk of the trunk component facilitates a smallerdelivery profile for the endovascular graft 10.

[0037] The sensors 16 may measure pressure, with the measurements usedas an aid in endovascular graft 10 placement or to identify anomaliesthat occur after endovascular graft 10 implantation but before aneurysmrupture occurs. The sensors 16 may detect changes in pressure resultingfrom blood leakage between the endovascular graft 10 and the vessel wall40, an endoleak resulting from an inadequate seal between them.Furthermore, the sensors 16 may detect changes in pressure resultingfrom leakage from an endoleak between the trunk 20 and vessel wall 40.Because sensors 16 are located in the area of the aneurysm sac 42, theremay be multiple sensors 16 disbursed over the graft material outer wallsince local thrombus or calcification may shield one or more of thesensors 16 from blood flow and render their measurements erroneous.Moreover, the sensors 16 may allow pressure differences throughout the“excluded” aneurysm sac 42 to be mapped. It is contemplated thatpressure measurements in the aneurysm sac may be obtained to an accuracyrange of ±1 to 30 mm Hg and preferably of ±10 mm Hg.

[0038] Alternatively, the sensors 16 may measure temperature.Differences in temperature may identify “hot spots” associated withinfection, inflammation, thrombus formation or other anomalies thatindicate an increased risk for aneurysm rupture. Methods known in theart of pathology and physiology may be used to relate temperature tochanges in the vessel walls within which the endovascular graft isimplanted.

[0039] Alternatively, the sensors 16 may detect blood flow by measuringoxygen or other constituents, such as enzymes, proteins and nutrients,which are altered by the presence of blood flow. Such sensors may allowdetection of minute blood flow, often missed by conventional imagingmodalities, and, therefore, allow endoleaks to be detected earlier. Onemethod is to obtain a baseline of the constituents upon implantation ofthe endovascular graft. Thereafter, changes in the amount of themeasured constituents may be used to identify anomalies.

[0040] Alternatively, the sensors 16 may measure electrical potential ormagnetic field strength. Changes in electrical potential may identifyareas of the patient's vasculature that are at risk for thrombusformation. Induced magnetic fields indicate motion at a charged portionof the aneurysm such as would occur from pulsatile pressure.

[0041] Sensors also may be provided to facilitate other sensingapplications such as blood oxymetry, blood glucose, blood or fluid flow,biochemical or hormonal balance, blood chemistry, positional data,dynamic displacement data, ocular pressure, respiration, electrophysiology, tissue stress, venous return and body acoustics.

[0042] Although shown external the limb component 30 in FIG. 1, it iscontemplated that the transmitter 12, power source 14 and sensors 16 maybe located internal the graft material of the limb component 30. It isfurther contemplated that the number of transmitters 12, power sources14 and sensors 16 shown in FIG. 1 may be varied to meet the requirementsof the individual patient. It is further contemplated that sensors 16which measure different pertinent parameters may be used together.Moreover, the invention shown in FIG. 1 may be utilized in any type ofendovascular graft implant known in the art.

[0043] Referring to FIG. 2, another embodiment of the invention is shownin which an integrated sensor/transmitter 50 is attached to theendovascular graft 110 and “satellite” sensors 52 are attached atvarious locations on the endovascular graft 110. The integratedsensor/transmitter 50 is capable of measuring a pertinent parameter aswell as transmitting measurements to a receiver (not shown) outside thatpatient's body. The “satellite” sensors 52 only measure pertinentparameters and their measurements are transmitted by the integratedsensor/transmitter, to which they are connected by leads 54. The“satellite” sensors 52 may provide a complete profile of pertinentparameters over the surface of the endovascular graft 110 and,therefore, facilitate better identification of anomalies.

[0044] Because the “satellite” sensors 52 are smaller than theintegrated sensor/transmitter 50, the overall bulk of the endovasculargraft 110 is smaller than if multiple integrated sensor/transmitterdevices 50 were utilized. Furthermore, the smaller “satellite” sensors52 may be placed such that measurements may be obtained from multiplelocations, such as near the superior attachment area or within theaneurysm sac 42. Moreover, the smaller “satellite” sensors 52 facilitatemeasurements from places on the endovascular graft 110 where local graftbulk is a constraint of the design, such as the contra limb, or near thesuperior attachment system that holds the graft in the patient's aorta.

[0045] A separate power source 114 may be provided. The power source canbe integrated into the sensor/transmitter as described previously andfurther below. The leads 54 which connect the integratedsensor/transmitter 50 to the “satellite” sensors 52 may be woven intothe graft fabric or attached external to the endovascular graft 110.

[0046] It is contemplated that the location and number of integratedsensor/transmitter devices 50, power sources 114 and “satellite” sensors52 shown in FIG. 2 may be varied to meet the requirements of theindividual patient. In the embodiment shown, the integratedsensor/transmitter device 50 is located at the crotch, thereby allowingit to be near the center of the aneurysm sac 42 (see FIG. 2) while stillbeing located furthest away from the aneurysm wall during shrinkage. Itis further contemplated that the invention shown in FIG. 2 may beutilized in any type of endovascular graft implant known in the art.

[0047] Moreover, the integrated sensor/transmitter 50 and “satellite”sensors 52 may be of any type known in the art used to measure pressure,temperature, oxygen and other blood constituents, electrical potentialor any other pertinent parameter indicative of endovascular graft orlumen health. One such integrated sensor/transmitter 50 to measurepressure is disclosed in U.S. patent application Publication No.2002/0045921 (Wolinsky et al.), the contents of which are herebyincorporated by reference. Again, other sensing applications may besupported such as blood oxymetry, blood glucose, blood or fluid flow,biochemical or hormonal balance, blood chemistry, positional data,dynamic displacement data, ocular pressure, respiration, electrophysiology, tissue stress, venous return and body acoustics.

[0048]FIG. 3 shows a typical integrated sensor/transmitter 50 for usewith the present invention. The integrated sensor/transmitter 50includes a control chip 55 with a transmitter/receiver, energy exchanger56, capacitor 57 and sensor 58. An external receiver (not shown) maycontain a transducer, computer, LCD display and measurement displaydevices, such as barometers if the sensor 58 measures pressure. Inoperation, the transducer in the external receiver charges the capacitor57 using ultrasonic energy and activates the sensor 58 to measure apertinent parameter and ultrasonically transmit the measured parameter.The external receiver receives the transmitted pertinent parameter,assesses the measurement and displays the measurement, for example, as apressure pulse curve.

[0049] Although FIG. 2 shows an integrated sensor/transmitter 50 and“satellite” sensors 52 connected by leads 54 and attached to theendovascular graft 110, alternate embodiments of the invention mayutilize an integrated sensor/transmitter 50 as the sole implant.Furthermore, the “satellite” sensors 52 may be attached to the vessel 40with the integrated sensor/transmitter 50 either attached to the vessel40 or attached to the endovascular graft 110. FIG. 4 shows anendovascular graft 110 implanted across an aneurysm sac 42 into which anintegrated sensor/transmitter 50 connected to “satellite” sensors 52 byleads 54 have been attached. It is contemplated that pressuremeasurements in the aneurysm sac 42 may be obtained to an accuracy rangeof ±1 to 30 mm Hg and preferably ±10 mm Hg utilizing either anintegrated sensor/transmitter 50 alone or in conjunction with one ormore “satellite” sensors 52 or integrated sensor/transmitters 50.

[0050] In an alternate embodiment of the invention illustrated in FIGS.2 and 4, micro devices having the capability to sense their locationrelative to each other are either attached to the endovascular graft 110or attached to the vessel 40. The micro devices may be excited by anexternal energy source, sense their relative location and transmit thedata to a receiver located outside the patient's body. The data may thenbe interpreted to determine if displacement of the endovascular graft110 or changes in the geometry of the vessel 40 has occurred. Suchchanges may provide early detection of endovascular graft 110displacement or aneurysm 42 re-dilation due to an endoleak. Additionalmicro devices could be provided for better resolution. Detectinglocation of the micro devices rather than measuring a pertinentparameter minimizes reliability problems due to encapsulation orthrombus isolation. It is contemplated that the micro devices may be anultrasonic crystal attached or integral to a MEM chip having the abilityto read, interpret and transmit data. The micro devices also may beultrasonic or other energy reflectors utilized in conjunction with anenergy source. Using ultrasound to show or image reflector locationwould be much easier than creating an ultrasound image of the tissue.

[0051] In a further embodiment of the invention illustrated in FIGS. 2and 4, devices or monuments which perform no sensing function may beattached to the implanted endovascular graft 110 or directly attached tothe aneurysm sac 42. The location of the monuments may be tracked with amonitoring device to detect changes in the position of the endovasculargraft 110 within the vessel 40 or changes in the geometry of the tissueoutside the endovascular graft 110. It is contemplated that themonitoring device may be located external the patient's body or attachedto an implanted endovascular graft. FIG. 5 illustrates an externalmonitoring device 54 being used to sense the location of an endovasculargraft 310 having monuments 60 attached thereto which has been implantedin a patient's body. It is contemplated that the monuments may beelectrically passive devices or magnetic sensors. The use of RF ormagnets to sense the position of monuments is contemplated.

[0052] In one example, the position of magnetic sensors attached to theaneurysm sac 42 are measured using an external magnet of known magneticfield strength and shape. By moving the external magnet to multiplepositions and orientations outside the body and polling the magneticsensors with ultrasound, a baseline of magnetic sensor positions isestablished. Subsequent polling of the magnetic sensor positions allowschanges in aneurysm sac 42 geometry to be detected.

[0053] In yet another embodiment of the invention shown in FIG. 6,sensors 16 or integrated sensor/transmitters 52 are attached to theendovascular graft 110 fabric using one continuous suture 70 with arunning stitch, from a starting point 72 on sensor 16, which continuesaround the sensor 16 and back to an end point 74 (the dashed lines inFIG. 6 indicate where the suture 70 is on the inner diameter of theendovascular graft 110 fabric). Suture loops 71 are provided on thesensor 16 to facilitate attachment. A single knot 75 may be used to jointhe ends of the suture 70. It is contemplated that the running stitchmay start and end at either end of the sensor and utilize more or lessstitches depending on the location of the sensor 16 on the endovasculargraft 110 and the attachment requirements. Minimizing the number ofknots not only reduces bulk but also reduces potential graft wear pointsand may allow the sensor to be placed close to the graft crotch due tothe lack of a knot at the distal end. It is further contemplated thatthe continuous suture 70 attachment method may be utilized with sensors16 having suture holes or any other attachment mechanism.

[0054] In yet another embodiment of the invention, the sensors 16 may becovered in a coating, such as Teflon or heparin, to inhibit tissuegrowth or covered in a coating, such as Thrombin, to promote a known orcontrolled amount of tissue growth. Inhibiting or controlling tissuegrowth, which may interfere with performance, increases the reliabilityof the measurements made by the sensors 16.

[0055] With reference to FIGS. 7 and 8, there is shown alternativestructure for attaching one or more of the previously describedsensor/transmitter devices, sensors, satellite sensors, monuments orother devices 202 to a graft component 204. Although shown attached to alimb component 206 via a tether or suture 208, the identifying,observing, transmitting or measuring devices 202 also can be attached byway of a tether 208 to a main body component 210 or other component. Infact, in certain circumstances, the particular device 202 can beimplanted in a vessel wall 220. Moreover, multiple devices 202 can beattached to a medical device in any desired pattern.

[0056] In one embodiment, the tether or suture 208 can embody a hardwire designed to maintain a distance between the identifying, observing,transmitting or measuring device 202 and the graft component 206, 210itself. In this way, the device 202 can be maintained in an aneurysmalsac 212, for example, allowing the graft 206, 210 to repair vasculaturewithout interference from the device 202. The hard wire tether 208 canbe configured to resist any forces that may urge the device 202 againstthe graft 206, 210, thereby minimizing possible wear on the graft 206,210 from the device 202.

[0057] In another embodiment, a bio-reabsorbable suture or tether 208can be employed to attach the identifying, observing, transmitting ormeasuring device 202 to a graft 206, 210 or other component. Afterdeployment of the graft 206, 210 within vasculature, the graft 206, 210becomes covered in clot and as the clot organizes, the bio-reabsorbabletether 208 breaks down. After the tether breaks down, the identifying,observing, transmitting or measuring device 202 is left in an aneurysmalsac 212 or in a position separate from the graft. The device 202 istherefore held in place by tissue that is generated as a result of theinterventional procedure. Again, the device 202 is held separate fromthe graft 206, 210 thereby minimizing wear to the graft.

[0058] As suggested, the device 202 can embody any of the previouslydescribed devices such as a sensor/transmitter, a sensor or satellitesensor, a monument or a power supply. The device 202 can therefore workindependently or in cooperation with any of the disclosed identifying,monitoring, sensing or transmitting devices.

[0059] While several particular forms of the invention have beenillustrated and described, it will be apparent that variousmodifications can be made without departing from the spirit and scope ofthe invention. For example, the structures and sensors described can beused with any medical device or in any acceptable area of a patient'sbody. Accordingly, it is not intended that the invention be limited,except as by the appended claims.

What is claimed:
 1. A prosthesis for repairing vasculature, comprising:a first prosthesis component; a tether; and a device having a measuringor transmitting capabilities, the device attached to the firstprosthesis component by the tether.
 2. The prosthesis of claim 1,wherein the tether is configured to maintain a distance between thefirst prosthesis component and the device after the device is placedwithin vasculature.
 3. The prosthesis of claim 1, wherein the tether isa hard wire tether.
 4. The prosthesis of claim 1, wherein the tether ismade of suture.
 5. The prosthesis of claim 1, wherein the tether isbio-reabsorbable.
 6. The prosthesis of claim 3, wherein the tetherbreaks down after clots form about the device to thereby hold the devicein place separate from the first prosthesis component.
 7. The prosthesisof claim 1, further comprising a second prosthesis component.
 8. Theprosthesis of claim 7, wherein the second prosthesis component isconfigured to mate with the first prosthesis component after the firstprosthesis component is placed within vasculature.
 9. The prosthesis ofclaim 8, wherein the first prosthesis component is configured to matewith the second prosthesis component after the second prosthesiscomponent is placed within vasculature.
 10. The prosthesis of claim 1,wherein the prosthesis is a modular graft assembly and the firstprosthesis component is one of a plurality of graft components.
 11. Theprosthesis of claim 10, wherein only the first graft prosthesiscomponent has the device attached thereto.
 12. The prosthesis of claim10, further comprising an additional device attached to more than onecomponent of the plurality of graft components.
 13. The prosthesis ofclaim 1, wherein the prosthesis is configured to treat an aneurysm andthe tether maintains the device within an aneurysm sac.
 14. Theprosthesis of claim 1, wherein the device is a sensor/transmitterassembly.
 15. The prosthesis of claim 1, wherein the device is a sensor.16. The prosthesis of claim 1, wherein the device is a satellite sensor.17. The prosthesis of claim 1, wherein the device is a monument.
 18. Theprosthesis of claim 1, wherein the device is a power supply.
 19. Theprosthesis of claim 1, wherein the device measures or cooperates tomeasure or identify blood constituents.
 20. The prosthesis of claim 1,wherein the device measures or cooperates to measure or identifypressure.
 21. The prosthesis of claim 1, wherein the device measures orcooperates to measure temperature.
 22. The prosthesis of claim 1,wherein the device measures or cooperates to measure oxygen.
 23. Theprosthesis of claim 1, wherein the first prosthesis component isbifurcated and includes a first limb and a second limb, the device isattached to one of the first and second limbs.